Why You Wake Up at 2–3 AM in Your 40s (Even with “Normal” Labs)

Waking at 2–3 AM in your 40s is not random — and it’s not just stress. In perimenopause, early-morning insomnia is often driven by neuroendocrine shifts involving cortisol rhythm changes, estrogen variability, progesterone decline, and altered autonomic regulation. These physiologic changes can precede abnormal lab results by years and may signal early cardiovascular and metabolic strain. Understanding why your brain becomes alert at 3 AM allows women to intervene earlier — stabilizing sleep, protecting metabolic health, and supporting heart function during midlife transition.